Field of the Invention
The present invention relates to cleaning apparatus for removing residual toner particles from a surface in, for example an electrostatographic reproduction machine such as a copier or printer. More particularly, the present invention relates to a magnetic roller-type cleaning apparatus for use in such machines.
Electrostatographic process reproduction machines such as copiers and printers for producing copies of an original document are well known. Such copies typically are produced on suitable receivers through a repeatable process that normally includes the steps of (1) using electrostatic charges in some manner to form a latent image on the surface of an image-bearing member; (2) developing the latent image with developer material that includes toner particles; (3) transferring the developed image to a suitable receiver for fusing; and (4) cleaning the image-bearing surface thereafter by removing residual toner and other particles therefrom in preparation for repeating the process steps.
The quality of the copies obtained by repeating these steps depends significantly on the effectiveness of cleaning devices or apparatus employed for removing the residual particles left on the image-bearing surface after the image transfer step. Such cleaning apparatus include, for example, magnetic roller cleaners as disclosed in U.S. Pat. Nos. 4,723,144 and 4,601,569.
Conventional magnetic roller cleaning apparatus as disclosed, for example, in U.S. Pat. No. 4,601,569 are well known for removing charged residual toner particles from the image-bearing surface. Typically, in such apparatus, a charged magnetic cleaning mix which includes magnetic carrier particles is moved within a housing by a magnetic roller into contact with oppositely charged residual toner particles on the surface being cleaned. The cleaning mix, as is well known, forms a nap on the magnetic roller. The bottom portion of such a nap is on and near the surface of the magnetic roller, and the top portion of such nap is extended radially away from such surface. After the nap makes contact with the surface being cleaned and picks up residual toner therefrom, the magnetic roller then rotates such nap into a detoning relationship with a detoning roller which is mounted spaced radially from the magnetic roller for removing the picked up residual toner particles from the nap.
It has been found that the detoning roller of such conventional apparatus removes residual toner particles mainly from the top portion of the nap on the magnetic roller, and removes very little of the residual toner particles from the bottom portion of such nap. The consequence is undesirable aging of residual toner particles in the bottom portion resulting in an undesirable stratification of cleaning mix properties forming the cleaning nap. Such properties include toner concentration, charge-to-mass ratio of particles, and particle polarity. The net result is ineffective cleaning of the surface and less than desired image quality.